Nm Diameter In Size Research Articles

Particle charging during pulsed EUV exposures with afterglow effect

Nanoparticle charging processes along with background spatial–temporal plasma profile have been investigated using 3D particle-in-cell simulations in a pulsed extreme ultraviolet (EUV) exposure environment. The particle charge polarity (positive or negative) strongly depends on its size, location, and background transient plasma conditions. The particle (100 nm diameter in size and conducting material) charge reaches a steady state in a single pulse (20 µs) within the EUV beams compared to particles outside the beam requiring multiple pulses. The larger the particle size, the lower the number of pulses required to reach a steady state. The charge of a particle decreases with pressure at a faster rate outside the beam compared to inside. These results are crucial for particle contamination (defectivity) control strategies for EUV lithography machines.

Application of mPEG-CS-cRGD/Bmi-1RNAi-PTX nanoparticles in suppression of laryngeal cancer by targeting cancer stem cells

Although surgery-based comprehensive therapy is becoming the main approach to treat laryngeal cancer, recurrence, metastasis, radiotherapy resistance and chemotherapy tolerance are still the main causes of death in patients. Targeted inhibition of laryngeal cancer stem cells has been considered as the consensus to cure laryngeal cancer. Our previous study has confirmed proto-oncogene Bmi-1 as a key regulator for self-renewal of laryngeal cancer stem cells. Targeted knockdown of Bmi-1 gene effectively inhibited the self-renewal and differentiation of laryngeal cancer stem cells, leading to the promoted sensitivity to chemotherapy including paclitaxel. However, due to off-target effects and quick degradation of the naked Bmi-1-RNAi small RNA oligo by nuclease in body fluids, it is urgently needed to develop a tumor-targeted delivery system with a protective shell. In this study, we designed and synthesized cRGD peptide-modified chitosan-polyethylene glycol slow-release nanoparticles (mPEG-CS-cRGD/Bmi-1RNAi-PTX) containing Bmi-1RNAi siRNA oligo and paclitaxel, which showed spherical in shape, 200 nm diameter in size, low cytotoxicity, strong DNA wrapping, resistance to nuclease degradation and high transfection efficiency to cells. Functional analysis indicated significant suppression of cell proliferation and migration and induction of apoptosis by the nanocomplex in laryngeal cancer cells in vitro. By application to the mouse model with laryngeal cancer, the nanocomplex inhibited tumor growth significantly in vivo. In addition, cRGD peptide, paclitaxel and Bmi-1 siRNA in the nanoparticles showed synergistic effects to suppress laryngeal cancer stem cells. In conclusion, this study not only developed a laryngeal tumor-targeted chemotherapeutic system, but also demonstrated a Bmi-1 RNAi-based chemotherapeutic strategy to inhibit cancer stem cells, having strong potential to treat laryngeal cancer patients suffering therapy resistance and/or tumor recurrence.

Antimicrobial Properties of Strychnos phaeotricha (Loganiaceae) Liana Bark Secondary Metabolites at the Interface of Nanosilver Particles and Nanoencapsulation by Chitosan Transport Vehicles

In this study, Strychnos phaeotricha liana bark extract was used as a metabolite container both on the surface of metallic nanosilver and encapsulated by a chitosan polymer. The plant extract was able to reduce Ag+ into Ag0 efficiently, and the encapsulation rate was determined. The synthesized nanoderivatives were characterized using ultraviolet‐visible spectrophotometry (UV‐Vis), Fourier transform infrared (FTIR) spectroscopy, powder X‐ray diffraction (PXRD), scanning electron microscopy (SEM), and energy dispersive X‐ray (EDX) spectroscopy. These methods allowed for the determination of grain size, elemental mapping, form, and the presence of secondary metabolites at the interface of the silver. Antimicrobial properties and the oral acute toxicity profile of the generated nanoderivatives were assessed. Overall, the results show plasmon resonance bands 380–550 nm in range and metabolites at the interface of a spherical nanosilver grain of 13.5 nm diameter in size. The hybrid nanosilver and encapsulated chitosan exhibited significant antimicrobial activity against Salmonella spp, Echerichia coli, and Candida spp. Both nanosilver grains and nanocapsules were found to be nontoxic at the tested doses and are potential models to prevent microbial resistance.

Green synthesis of ZnO nanoparticles using loquat seed extract; Biological functions and photocatalytic degradation properties

This research aimed to optimize the loquat (Eriobutria japonica) seed aqueous extract mediated green synthesis of zinc oxide nanoparticles (ZnO NPs) through Response Surface Methodology (RSM). The independent variables including zinc acetate concentration (0.01–0.2 M), the precursor to the extract ratio (1: 2.5 to 1: 10) and pH value (8–12.5) affected the particle size and the absorption content. Microscopic study and spectroscopic examination demonstrated NPs <50 nm diameter in size with good absorption at 349 nm. The optimized ZnO NPs were characterized by XRD (X-ray diffraction), EDX (Energy-dispersive X-ray spectroscopy) and FTIR (Fourier-transform infrared spectroscopy). The results showed that ZnO NPs with a crystalline nature and hexagonal wurtzite structure could be stabilized and capped by the presence of functional groups in the seed extract. Antibacterial study of these NPs against some food pathogens depicted a higher bactericidal activity on Gram-positive Staphylococcus aureus in a dose-dependent manner. Concentration-dependent antioxidant activity was also observed for NPs in the FRAP assay. Evaluation of photocatalytic activity revealed that the highest degradation of methylene blue (MB) was achieved with an initial NP concentration of 12 mg/mL under UV light.

Efficient biogenesis of ZnO nanoparticles using extracellular extract of Saccharomyces cerevisiae : Evaluation of photocatalytic, cytotoxic and other biological activities

This research aimed to synthesize zinc oxide nanoparticles (ZnO NPs) using an extracellular extract of Saccharomyces cerevisiae. The physical characteristics of the biosynthesized NPs were studied using XRD, FTIR, FESEM, and EDS. Microscopic study and spectroscopic examination depicted spherical ZnO NPs < 30 nm diameter in size, relatively stable, and bearing a hexagonal phase. Antibacterial study of these NPs against food pathogens showed enhanced higher antibacterial activity on Staphylococcus aureus in a dose-dependent manner. Concentration-dependent antioxidant activity was also observed for ZnO NPs in both DPPH and FRAP assay. Also, the anticancer study of these NPs against MCF-7 cancer cell line demonstrated a considerable cytotoxic effect in a concentration-dependent manner. Evaluation of photocatalytic activity indicated that the highest removal of MB was achieved to be 67% with an initial ZnO NP concentration of 12 mg/mL under UV light. The results suggested the biosynthesis of ZnO NPs in a cost-less approach which can be lead to sustainable development for its use as photocatalyst and anti-cancer therapeutic agents.

Facile green synthesis of zinc oxide nanoparticles using Thymus vulgaris extract, characterization, and mechanism of chromium photocatalytic reduction

Zinc oxide nanoparticles (ZnO NPs) were synthesized via a green and simple method using extract of Thymus vulgaris (TV). The green synthesized zinc oxide nanoparticles (GZnO NPs) were characterized by field emission scanning electron microscope (FE-SEM), energy dispersive spectroscopy (EDS), transmission electron microscope (TEM), Ultra violet-visible diffuse reflectance spectra (UV–vis-DRS), and Fourier Transform Infra-Red )FTIR( spectrophotometer.The results of various analyses confirmed the formation of GZnO NPs. UV–vis spectrum exhibited a blue shift absorption peak at 368 nm and the band gap energy was calculated 3.4 eV. FTIR study suggested that polyphenols and other bio-chemicals were responsible for reduction and stabilization of synthesized ZnO NPs. FE-SEM and TEM images showed particles with spherical shape and less than 40 nm diameter in size. In the photocatalytic reduction study, effect of some important variables such as catalyst dosage, methanol hole scavenger, contact time, and Cr(VI) concentration was investigated. To study photocatalytic activity of GZnO NPs, the adsorption control (AP) and photolysis (PP) experiments were conducted in same condition of photocatalytic process (PCP). Synergistic effect of PCP showed the high activity of GZnO NPs as catalyst for Cr(VI) reduction in the photocatalytic reactor (about 83% at 15 min, 0.5 mg l−1 of Cr(VI) and 0.015 g l−1 of GZnO NPs concentration). EDS analysis confirmed the presence of chromium on GZnO after adsorption control and photocatalytic processes. Kinetic constant for Cr(VI) reduction by PCP and PP obtained 0.154 and 0.008, which confirmed the increasing removal efficiency of chromium in the present of GZnO in photo-reactor as catalyst under UV light.

From Concentrated Dispersion to Solid β‐Cyclodextrin Polymer‐Capped Silver Nanoparticle Formulation: A Trojan Horse Against Escherichia coli

AbstractPreparation of concentrated silver nanoparticles in water remains a challenge today. The intrinsic reactivity of silver, as well as the high surface energy of nanoparticles, make it difficult to handle them without altering their pristine properties. Herein, we report the preparation of concentrated silver nanoparticles (AgNPs) dispersion (2 mM; 1.5⋅1015 NPs/mL) by reducing Ag+ in‐situ of a β‐cyclodextrin‐epichlorohydrin polymer (βCDP) as a capping agent. The prepared nanoparticles (AgNPs@βCDP) with a Surface Plasmon Resonance band at 396 nm, and a hydrodynamic diameter of 21.4 ±1.8 nm, retained both features after being precipitated and re‐dispersed in water. The AgNPs core had a spherical morphology, with a 12.7 ±1.5 nm diameter in size, as determined by TEM. The AgNPs@βCDP showed outstanding bactericidal properties against Escherichia coli (MIC= 0.37 nM), one of the lowest ever achieved for silver nanoparticles. We suggest that the polymer acts as a Trojan horse with AgNPs as payload.

Urea-Driven Epigallocatechin Gallate (EGCG) Permeation into the Ferritin Cage, an Innovative Method for Fabrication of Protein-Polyphenol Co-assemblies.

The 8 nm diameter cavity endows the ferritin cage with a natural space to encapsulate food components. In this work, urea was explored as a novel medium to facilitate the formation of ferritin-polyphenol co-assemblies. Results indicated that urea (20 mM) could expand the 4-fold channel size of apo-red bean ferritin (apoRBF) with an increased initial iron release rate υ0 (0.22 ± 0.02 μM min-1) and decreased α-helix content (5.6%). Moreover, urea (20 mM) could facilitate the permeation of EGCG into the apoRBF without destroying the ferritin structure and thus form ferritin-EGCG co-assemblies (FECs) with an encapsulation ratio and loading capacity of 17.6 and 2.1% (w/w), respectively. TEM exhibited that FECs maintained a spherical morphology with a 12 nm diameter in size. Fluorescence analysis showed that urea intervention could improve the binding constant K [(1.22 ± 0.8) × 104 M-1] of EGCG to apoRBF. Furthermore, the EGCG thermal stability was significantly improved (20-60 °C) compared with free EGCG. Additionally, this urea-involved method was applicable for chlorogenic acid and anthocyanin encapsulation by the apoRBF cage. Thus, urea shows potential as a novel potential medium to encapsulate and stabilize bioactive polyphenols for food usage based on the ferritin protein cage structure.

Understanding energy transfer with luminescent gold nanoclusters: a promising new transduction modality for biorelated applications.

Ultrasmall noble metal and especially gold nanoclusters (AuNCs, ≤2 nm diameter in size) display a range of unique quantum confined and photophysical properties which are far different from their larger-sized nanoparticle counterparts or that of the bulk parent material. Amongst these properties, the photoluminescence of gold AuNCs has stimulated much interest for biological applications due to a combination of their small size, high photostability and range of emissions depending on size and surface stabilizing ligands, including near-IR emission. The dearth of robust Förster resonance energy transfer (FRET) donors and acceptors available to populate the latter spectral range is also driving strong interest in applying AuNCs for similar utility and especially for biosensing. However, the exact mechanism of how AuNCs engage in this type of energy transfer (ET) is still not defined and accumulating evidence indicates that it is not by a classical Förster process although, interestingly, many of the same characteristics and photophysical requirements seem to be present and even many-times required. Here, we summarize the state of the art in AuNC ET studies with a special emphasis on relevance to biological utility ranging from diagnostics to distance measurements along with describing the different ET mechanisms that have been ascribed with their use. Due to its corresponding importance in this discussion, we provide a brief overview of how these materials are synthesized, the current understanding of how their photoluminescence originates, and some related information on silver nanocluster (AgNC) ET along with related processes such as chemically-induced ET. A perspective and outlook on how this area will develop in the future is also provided.

Novel polyacrylate-based cationic nanoparticles for survivin siRNA delivery combined with mitoxantrone for treatment of breast cancer

As a gene delivery method in breast cancer therapy, knocking down the undesired genes in the cancerous cells would be promising. Inhibitors of Apoptosis Protein (IAP) family genes are some of the genes whose responsibility is inhibition of apoptosis in cells. Silencing these genes seems to be helpful directing the tumor cells to death. siRNA sequence designed against survivin anti-apoptotic gene can play this role if carried to the cytoplasm. Here we prepared a positive charged biocompatible nano-sized particle made up of a Fe3O4 core covered respectively by polyacrylate (PA) and polyethyleneimine (PEI) layer, which could successfully deliver the siRNA into the MCF-7 cells. The particle structure was checked and having less than 50 nm diameter in size, positive charge and, safety towards MCF-7 cells besides being able to form nanoplexes with the siRNA strand helps it entering into the biologic assays part. The siRNA delivery evaluated via flowcytometry. Apoptosis induction was determined by DAPI staining. The efficiency of survivin gene knockdown was evaluated in mRNA and protein levels using Real time PCR and western blotting methods. Overall, the Fe3O4-PA-PEI nanoparticles can deliver siRNA effectively into the cytoplasm of the MCF-7 breast cancer cells and induce apoptosis.

Resveratrol-loaded Nanoparticles Induce Antioxidant Activity against Oxidative Stress.

Resveratrol acts as a free radical scavenger and a potent antioxidant in the inhibition of numerous reactive oxygen species (ROS). The function of resveratrol and resveratrol-loaded nanoparticles in protecting human lung cancer cells (A549) against hydrogen peroxide was investigated in this study. The 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid (ABTS) assay was performed to evaluate the antioxidant properties. Resveratrol had substantially high antioxidant capacity (trolox equivalent antioxidant capacity value) compared to trolox and vitamin E since the concentration of resveratrol was more than 50 μM. Nanoparticles prepared from β-lactoglobulin (β-lg) were successfully developed. The β-lg nanoparticle showed 60 to 146 nm diameter in size with negatively charged surface. Non-cytotoxicity was observed in Caco-2 cells treated with β-lg nanoparticles. Fluorescein isothiocynate-conjugated β-lg nanoparticles were identified into the cell membrane of Caco-2 cells, indicating that nanoparticles can be used as a delivery system. Hydrogen peroxide caused accumulation of ROS in a dose- and time-dependent manner. Resveratrol-loaded nanoparticles restored H2O2-induced ROS levels by induction of cellular uptake of resveratrol in A549 cells. Furthermore, resveratrol activated nuclear factor erythroid 2-related factor 2-Kelch ECH associating protein 1 (Nrf2-Keap1) signaling in A549 cells, thereby accumulation of Nrf2 abundance, as demonstrated by western blotting approach. Overall, these results may have implications for improvement of oxidative stress in treatment with nanoparticles as a biodegradable and non-toxic delivery carrier of bioactive compounds.

Low-dose AgNPs reduce lung mechanical function and innate immune defense in the absence of cellular toxicity

Multiple studies have examined the direct cellular toxicity of silver nanoparticles (AgNPs). However, the lung is a complex biological system with multiple cell types and a lipid-rich surface fluid; therefore, organ level responses may not depend on direct cellular toxicity. We hypothesized that interaction with the lung lining is a critical determinant of organ level responses. Here, we have examined the effects of low dose intratracheal instillation of AgNPs (0.05 μg/g body weight) 20 and 110 nm diameter in size, and functionalized with citrate or polyvinylpyrrolidone. Both size and functionalization were significant factors in particle aggregation and lipid interaction in vitro. One day post-intratracheal instillation lung function was assessed, and bronchoalveolar lavage (BAL) and lung tissue collected. There were no signs of overt inflammation. There was no change in surfactant protein-B content in the BAL but there was loss of surfactant protein-D with polyvinylpyrrolidone (PVP)-stabilized particles. Mechanical impedance data demonstrated a significant increase in pulmonary elastance as compared to control, greatest with 110 nm PVP-stabilized particles. Seven days post-instillation of PVP-stabilized particles increased BAL cell counts, and reduced lung function was observed. These changes resolved by 21 days. Hence, AgNP-mediated alterations in the lung lining and mechanical function resolve by 21 days. Larger particles and PVP stabilization produce the largest disruptions. These studies demonstrate that low dose AgNPs elicit deficits in both mechanical and innate immune defense function, suggesting that organ level toxicity should be considered.

Magnetic Nanofluid Applications in Electrical Engineering

This paper presents a superparamagnetic nanofluid (SMP-NF) and three of its applications. The SPM-NF particles were suspended in oleic acid as surfactant, and then dispersed in UTR 40 transformer oil (TO). The average particle size obtained from X-ray diffraction is 14 nm, and from scanning electron microscopy is between 10 and 30 nm. The magnetic measurements for the oleic-oil transformer acid-magnetite nanoparticles of 27 nm diameter in size and 9.78×1025 nanoparticles/m3 particle density system provide for specific saturation magnetization, Ms. The volume fraction is 1.1% and the magnetization is 62 Gs. The SPM-NF may be designed to be used either as coolant or as magnetic medium in three electrotechnic devices: a power electric transformer TMOf 2-36 kV-40 kVA, at 50 Hz, a microactuator that implements the pulse width modulation (PWM) principle, and in miniature planar spiral transformers, for galvanic separation or step-up/step-down conversion. The paper presents experimental and numerical simulation results that confirm that the SPM-NF usage open new venues in optimizing conventional electrotechnic constructions or to design novel devices.

A study of new particle formation in the marine boundary layer over the central Arctic Ocean using a flexible multicomponent aerosol dynamic model

ABSTRACTEnhancement of number concentrations of particles with sizes less than 25 nm diameter has been frequently observed in the boundary layer over the central Arctic Ocean during summer. The sectional aerosol dynamics model for Marine Aerosol Formation (MAFOR) was applied to evaluate the capability of different nucleation mechanisms to reproduce nucleation events observed during three expeditions (1996, 2001 and 2008) onboard the Swedish icebreaker Oden. Model calculations suggest that a source rate of a condensable organic vapour (OV) of about 2×105 cm−3 s−1 is required to reproduce observed growth of nucleation mode particles. Nucleation rates predicted by the newly proposed combined sulphuric acid nucleation mechanism, which best described new particle formation in the Arctic, ranged from 0.04 to 0.1 cm−3 s−1. This mechanism additively combines ion-mediated nucleation and cluster activation, and treats condensation of OV without correction of the Kelvin effect. In several events, the simultaneous number enhancement of particles in the 20–50 nm size range remained unexplained by the nucleation mechanisms. This lends support to alternative theories such as the fragmentation of marine gels (≈200–500 nm diameter in size) by physical or chemical processes.

Characterization of aqueous dispersions of Fe 3O 4 nanoparticles and their biomedical applications

A newly developed non-polymer coated Fe 3O 4 nanoparticles showing well-dispersion were synthesized using Fe(II) and Fe(III) salt chemical coprecipitation with tetramethylammonium hydroxide (N(CH 3) 4OH) in an aqueous solution. Transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectrometer (FT-IR), X-ray photoelectron spectrometer (XPS) and superconducting quantum interference measurement device (SQUID) measurements were employed to investigate the iron oxide properties. The resulting iron oxide particles were manipulated to be as small as 9 nm diameter in size. Based on FT-IR and X-ray photoelectron spectrometer results, it is suggested that the surfaces of the magnetite (Fe 3O 4) particles are covered with hydroxide (–OH) groups incorporated with (CH 3) 4N + through electrostatic interaction. The in vitro cytotoxicity test revealed that the magnetite particles exhibited excellent biocompatibility, suggesting that they may be further explored for biomedical applications. NMR measurements revealed significantly reduced water proton relaxation times T1 and T2. The MR images of the nanoparticles in water, serum, and whole blood were investigated using a 1.5 T clinical MR imager. Significant reduction of the background medium signal was achieved in the T2-weighted and the T2 *-weighted sequence especially in the serum and whole blood. Combining the advantage of MRI signal contrast, the non-polymer-coated surface chemistry for distinct bioconjugation and the homogenous nanometer size for better controlled biodistribution, these preliminary experiments demonstrated the potential of the as-synthesized magnetite material in functional molecular imaging for biomedical research and clinical diagnosis.

Investigating filopodia sensing using arrays of defined nano-pits down to 35 nm diameter in size

In order for cells to react to topography, they must be able to sense shape. When considering nano-topography, these shapes are much smaller than the cell, but still strong responses to nano-topography have been seen. Filopodia, or microspikes, presented by cells at their leading edges are thought to be involved in gathering of special information. In order to investigate this, and to develop an understanding of what size of feature can be sensed by cells, morphological observation (electron and fluorescent microscopy) of fibroblasts reacting to nano-pits with 35, 75 and 120 nm diameters has been used in this study. The nano-pits are especially interesting because unlike many of the nanofeatures cited in the literature, they have no height for the cells to react to. The results showed that cell filopodia, and retraction fibres, interacted with all pit sizes, although direct interaction was hard to image on the 35 nm pits. This suggests that cells are extremely sensitive to their nanoevironment and that should be taken in to consideration when designing next-generation tissue engineering materials. We suggest that this may occur through nanocontact guidance as filopodia are moved over the pits.

Electrochemical in situ STM study of Al and Ti–Al alloy electrodeposition on Au(111) from a room temperature molten salt electrolyte

The electrodeposition of Al and Ti–Al alloys on Au(111) from an acidic aluminium chloride-1-methyl-3-butylimidazolium chloride (AlCl3–MBImC) room-temperature molten salt electrolyte containing TiCl4 was studied by cyclic voltammetry and chronoamperometry and in particular, nucleation and growth processes were monitored in situ by means of electrochemical scanning tunneling microscopy (EC-STM) for the first time. Two underpotential deposition (UPD) states for Al were observed in the cyclic voltammogram at 0.51 and +0.22 V vs. Al/Al3+. At corresponding UPD conditions STM images show different nucleation behavior for Al: first a growth of clusters all over the Au surface, and later preferentially along the step edges leading to a step edge decoration. Potential step experiments imply progressive nucleation and growth and are evidenced by STM images obtained at different time intervals showing the growth of Al clusters of up to 8 nm diameter in size. After anodic dissolution of the deposited Al film, the appearance of circular holes of a size comparable with the Al clusters notably along Au step edges indicates Al–Au surface alloy formation. Tunneling current vs. bias voltage (I–U) curves of the Al clusters exhibit a reduced tunneling barrier height (Φ) of 0.23 eV. A distinct two-dimensional nucleation of Ti–Al clusters begins to occur at 0.5 V vs. Al/Al3+ exclusively on the Au terraces. They grow in the form of chains reaching a size of about 2–3 nm diameter in size, smaller in comparison with Al clusters. X-Ray photoelectron spectra of the potentiostatically deposited film under overpotential deposition (OPD) conditions confirm the formation of a Ti–Al alloy phase.

FCC and BCC Solidification Products in a Rapidly Solidified Austenitic Steel.

ABSTRACTThe microstructures and local composition variations in centrifugally atomized high-sulfur stainless steel powder are investigated. Both fcc and bcc are found to be primary solidification phases in the as-solidified powder of this nominally austenitic steel where the smaller powder particles (≲ 70 micron diameter) tend to be bcc.Cellular solidification structures, with sulfide precipitates (100 to 200 nm diameter in size) at the cell walls, are observed in both fcc and bcc particles. The bcc structure, however, has many small sulfide precipitates (10 to 20 nm diameter) in the cell interior with few larger sulfide precipitates at the cell walls. The small precipitates, observed only in the bcc structures, form on cooling from a supersaturated solid solution that results from reduced solute partitioning during solidification. Partitioning of chromium and nickel is minimal in these cellular structures. A non-cellular bcc structure is also observed with small sulfide precipitates throughoutthe entire structure. This non-cellular bcc structure results from smooth-front massive solidification. Analysis of the nucleation process for solidification indicates that a transition from fcc nucleation to bcc nucleation occurs with increasing wetting angle in heterogeneous nucleation. Thus bcc should nucleate in the smaller droplets of a liquid dispersion where catalytic surfaces of low potentcy (large wetting angle) tend to be the only heterogeneous nucleants available.